Potassium channels play an integral role in regulating the activity of excitability of cells such as nerve and muscle. When potassium channels are open, potassium flows down its concentration gradient from inside to outside the cell. This draws the membrane away from the firing threshold and thereby decreases cell excitability. The opening and closing of voltage dependent potassium channels is regulated by the membrane potential channels open as the membrane is depolarized. The voltage dependence of channel opening arises from conformational changes in which there is a net movement of charge across the electric field of the membrane. This charge movement can be measured as a transient "gating currents" in voltage clamp experiments. The long term goal of this proposal is to define the structural domains that couple this charge movement to the opening and closing of voltage dependent potassium channels. This proposal focuses on two main aspects: 1) pharmacological agents that interact with the gating mechanism of voltage dependent potassium channels and 2) two potassium channel clones that couple differently charge movement and channel closing as assayed by internal tetraethylammonium. The experiments employ both the patch clamp and cut open oocyte Vaseline gap techniques to measure ionic and gating current from cloned potassium channels. These studies should provide meaningful insight to the mechanisms by which potassium channel activity is modulated by membrane potential and may reveal mechanisms for their regulation.